By Hajime Kanamori, MD, PhD, MPH, Division of Infectious Diseases, University of North Carolina

Hajime Kanamori, MD, PhD
Hajime Kanamori, MD, PhD

We reviewed outbreaks of waterborne healthcare-associated infections as well as prevention strategies and control measures for each water reservoir (Table).

  • Hospital water sources may serve as a reservoir of healthcare-associated pathogens.
  • The common waterborne pathogens were bacteria, including Legionella and other gram-negative bacteria, and nontuberculous mycobacteria.
  • These waterborne pathogens caused a variety of infections, including bacteremia and invasive and disseminated diseases, particularly among immunocompromised hosts and critically ill adults as well as neonates.
  • Waterborne outbreaks occurred in healthcare settings with emergence of new reported reservoirs, including electronic faucets (Pseudomonas aeruginosa and Legionella), decorative water wall fountains (Legionella), and heater-cooler devices used in cardiac surgery (Mycobacterium chimaera).
  • With emergence of reservoirs and pathogens that have been unrecognized so far, waterborne healthcare-associated outbreaks and infections continue to occur and affect patients’ health and safety.
  • Advanced molecular techniques are useful for achieving a better understanding of reservoirs and transmission pathways of waterborne pathogens.
  • It is important for healthcare personnel to understand reservoirs of waterborne pathogens for developing prevention strategies and control measures of healthcare-associated infections.

See summary of key issues and infection prevention strategies:

Table. Summary of key issues and infection prevention strategies against waterborne outbreaks by water reservoir in healthcare settings.

Reservoir Key issues Infection prevention strategies
Potable water, tap water, and hospital water systems Potable water is not sterile, and pathogenic waterborne organisms may exist in potable water at acceptable levels of coliform bacteria (<1 coliform bacterium/100 mL).
Healthcare-associated outbreaks have been linked to contaminated potable water.
Semicritical devices are often rinsed with potable water, which may lead to contamination of the equipment and subsequent healthcare-associated infections.
Common pathogens include non-enteric Gram-negative bacilli (e.g., P. aeruginosa), Legionella, NTM.
Follow public health guidelines.
Hot water temperature at the outlet at the highest temperature allowable, preferable >124oF.
Water disruptions: post signs and do not drink tap water.
Maintain standards for potable water (<1 coliform per 100 mL).
Rinse semi-critical equipment with sterile water, filtered water, or tap water followed by alcohol rinse.Some experts have recommended periodic monitoring of water samples for growth of Legionella.Legionella eradication can be technically difficult, temporary, and expensive.Potential methods of eradication include filtration, ultraviolet, ozonization, heat inactivation (>60oC), hyperchlorination, and copper-silver ionization (>0.4 ppm and >0.04 ppm, respectively).
Sinks Colonization of sinks with Gram-negative bacilli has been reported.
Some studies demonstrate a transmission link between a colonized sink and infected patients.
Some studies describe that multidrug-resistant Gram-negative bacilli are associated with contaminated sinks.
Gram-negative bacilli can survive wet environments, including sinks, for a long time (>250 days)
Transmission can be caused by splashing of water droplet from contaminated sinks to hands of healthcare personnel, followed by transient colonization of hands.
Common pathogens include Gram-negative bacilli (e.g., Pseudomonas, Acinetobacter, Serratia).
Use separate sinks for handwashing and disposal of contaminated fluids.
Decontaminate or eliminate sinks as a reservoir if epidemic spread of Gram-negative bacteria via sinks is suspected.
Faucet aerators Faucet aerators may serve as a platform for accumulation of waterborne pathogens.
Potential pathogens include Pseudomonas, Stenotrophomonas, and Legionella.
Routine screening and disinfection or permanent removal of all aerators are not warranted at present.
No precautions necessary at present.
For Legionella outbreaks, clean and disinfect faucet aerators in high risk patient areas periodically, or consider removing them in the case of additional infections.
Showers Some outbreaks are linked to contaminated shower heads or inhalation of aerosols.
Potential pathogens include Legionella, Pseudomonas, NTM, Group A streptococcus, and Aspergillus.
Prohibit use of showers in neutropenic patients
Control Legionella colonization of potable water.
Ice and ice machines Patients can acquire pathogens by sucking on ice, ingesting iced drinks, or use of contaminated ices for cooling medical procedure and patients’ skin.
Large outbreaks occurred when ice machines have become contaminated and ice used for cooling drinking water.
Common pathogens include Pseudomonas, Enterobacter, Legionella, NTM, and Cryptosporidium.
Do not handle ice by hand.

Do not store pharmaceuticals or medical solutions on ice for consumption.
Use automatic dispenser rather than open chest storage compartments in patient areas.
Clean and disinfect ice-storage chests regularly.
Meaningful microbial standards for ice and ice machines do not exist.
Routine culturing of ice machines are not recommended.
A regular disinfection program for ice machines is recommended.

Eyewash stations Stationary and portable eyewash stations may not be used for months or years.
The water source may stand in the incoming pipes at room temperature for a long period.
Pathogens, including Pseudomonas, Legionella, amoebae, and fungi, could be transmitted.
Use sterile water for eye flush or regularly (e.g. monthly) flush eyewash stations
Dental-unit water systems Potable water usually supplies dental units.
Water delivered to dental devices (e.g. dental handpieces and air/water syringes) as well as dental unit water lines may be contaminated.
Immunocompromised patients may be at risk for infection.
Pathogens, including Sphingomonas, Pseudomonas, Acinetobacter, Legionella, and NTM, have been recovered from water supplies in dental-units.
Clean dental water systems.
Flush with water and disinfectant solution, or use of clean-water systems that put sterile water into the dental unit.
Flush dental instruments with water and air for 20-30s from any dental device connected to the dental water system that enters the patient’s mouth (e.g., handpieces).
Ensure that water in dental unit meets standards (<500 CFU/ml).
Dialysis water Excessive levels of Gram-negative bacilli in the dialysate were responsible for pyrogenic reactions in patients or bacteremia, which was caused by bacteria or endotoxin entry into the blood from the contaminated dialysate. Follow AAMI standards for quality assurance performance of dialysis devices.
Disinfect water distribution system on a regular basis.
Perform microbiological testing and endotoxin testing for water in dialysis settings regularly.
Maintain dialysis water (input) <200 CFU/mL and dialysate (output) <200 CFU/mL per CMS.
Water and ice baths Contaminated water baths were used to thaw or warm blood products (fresh plasma, cyroprecipitate) or peritoneal dialysate bottles, followed by contamination of the infusates occurred during preparation.
Contaminated ice baths were used to cool syringes or bottles of saline in measuring cardiac output.
Potential pathogens include Pseudomonas, Acinetobacter, Burkholderia, Staphylococcus, and Ewingella.
Consider routine cleaning, disinfection, and changing of water in water baths.
Add germicide to water bath or use plastic overwrap of blood products and keep the surfaces dry.
Use sterile water in ice baths (or at room temperature) used for thermodilution catheters.
Bathing, tub immersion, and hydrotherapy Tub immersion used in hospitals for physical hydrotherapy and for cleaning of burn wounds can cause cross-transmission, transmission from environmental reservoirs, or autotransmission.
Skin infections such as folliculitis and cellulitis occurred related to water immersion.
Water contamination of central venous catheters during bathing was related to bloodstream infection.
Potential pathogens include Pseudomonas, Enterobacter, Citrobacter, Acinetobacter, Legionella, Alcaligenes, and NTM.
Adhere strictly to proper disinfection of tub between patients.
Drain and clean tanks and tubs after use of each patient, and disinfect surfaces and components according to the manufacturer’s instructions.
Add disinfectant to the water: 15 ppm in small hydrotherapy tanks and 2-5 ppm in whirlpools per CDC.
Disinfect after using tub liners.
Cover catheter sites with transparent occlusive dressing.
Toilets Transmission can be caused by aerosolization of fecal bacteria via flushing or surface contamination by fecal bacteria.
Transmission could happen in healthcare facilities caring for mentally or neurologically impaired patients, or children.
Potential pathogens include enteric bacteria, Pseudomonas, C. difficile, and norovirus
Facilitate good handwashing practices.
Maintain clean surfaces with disinfectants.
Clean bowl with a scouring powder and a brush.
No reason to pour disinfectant into bowl.Separate toilet bowl from clean hospital surfaces
Flowers and vases Flower vases and potted plants are heavily colonized with potential pathogens, including Acinetobacter, Klebsiella, Enterobacter, Pseudomonas, Serratia, B. cepacia, A. hydrophilia, and Flavobacterium.
No healthcare-associated outbreaks directly linked to flower vases or potted plants have been reported.
Prohibit fresh flowers and potted plants in the rooms of immunocompromised and ICU patients.
Or add antimicrobial agent to vase water and disinfect vases after use.
Electronic faucets Electronic faucets were likely to be contaminated by several waterborne pathogens than handle-operated faucets.
Issues associated with electronic faucets include a longer distance between the valve and the tap, resulting in a longer column of stagnant, warm water, which favors production of biofilms; reduced water flow; reduced flushing effect (growth favored); valves and pipes made of plastic (enhances adhesion of P. aeruginosa).
Electronic faucets need to be designed so that they do not promote the growth of microorganisms.
No guideline (but some authors have recommended) to remove electronic faucets from high-risk patient care areas [e.g., BMTU]).
Some have recommended periodic monitoring of water samples for growth of Legionella.
Decorative water wall fountains Legionella pneumonia cases associated with decorative water fountain were reported.
There is an unacceptable risk in hospitals serving immunocompromised patients (even with standard maintenance and sanitizing methods).
Avoid installation, especially in healthcare facilities serving immunocompromised patients or in areas caring for high risk patients.
Perform maintenance regularly and monitor water safety strictly unless removed.
Heater-cooler units Healthcare-associated M. chimaera outbreak due to heater-cooler units during cardiac surgeries as a water source has been recently reported.
Airborne transmission from contaminated heater-cooler unit water tanks.
Ensure that heater-cooler units are safe and properly maintained according to the manufacturer’s instructions.
Enhance vigilance for NTM infections in patients after cardiac surgeries using heater-cooler devices.
If NTM infections are suspected, review microbiology database (NTM-positive cultures) and medical records of surgical procedures within several years after cardiac surgeries.
Miscellaneous Potential reservoirs include distilled water or containers (outbreaks with E. cloacae and B. cepacia), wash basins (Salmonella urbana infection, Trichosporon asahii infection, Legionella pneumonia), intraaortic balloon pump (B. cepacia bacteremia), humidifier water in ventilator systems (Acremonium kiliense postoperative endophthalmitis), water cooler (gastrointestinal illness), holy water (A. baumannii infection), deionized water (Exophiala jeanselmei fungemia), water-damaged plaster (mucormycosis), water birth (Legionella pneumonia), water-saving device (P. aeruginosa infection), rinse water during endoscope reprocessing (Gram negative bacteria). Consider control measures based on risk assessment by each reservoir when available.


The information used in this table is based on references in this review. The infection prevention and control was updated from our previous review [Infect Control Hosp Epidemiol 1997; 18:609–16] and recommendations from CDC and the Healthcare Infection Control Practices Advisory Committee [MMWR Recomm Rep 2003; 52(RR-10):1–48]. Abbreviations: AAMI, Association for the Advancement of Medical Instrumentation; BMTU, bone marrow transplant unit; CDC, Centers for Disease Control and Prevention; CFU, colony-forming unit; CMS, Centers for Medicare and Medicaid Services; ICU, intensive care unit; NTM, nontuberculous mycobacteria.

Retrieved from:

Kanamori H, Weber DJ, Rutala WA. Healthcare Outbreaks Associated With a Water Reservoir and Infection Prevention Strategies. Clin Infect Dis. 2016;62(11):1423-35.


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